The present invention relates to a double-acting hydraulic jack which also has shock-absorbing functions.
Jacks of this type are known and consist of a cylinder assembly in which a piston can move, the piston being connected to an actuated rod and defining in the cylinder, on one side, a first actuating chamber for bringing the piston into the working position, provided with a first inlet for actuating liquid and connected to an accumulator of elastically variable volume, and, on the other side, a second actuating chamber for retracting the piston from its working position and provided with a second inlet for actuating liquid.
A disadvantage of this system is that in the event of a shock being applied to the actuated rod the rapid displacement of the piston generates an abrupt pressure drop in the second actuating chamber, thus risking producing an inflow of the external fluid surrounding the jack into the second actuating chamber. This risk is particularly great when the jack is submerged in an expanse of water, such as the sea, at a depth generating a high hydrostatic pressure.
This disadvantage can be mitigated by associating with the jack additional hydraulic equipment which, in the event of a shock, ensures that actuating liquid is supplied rapidly to the second actuating chamber, but this makes installation considerably more complicated.